FizzBuzzを書いたことがないとまずいらしいので・・・

fizzbuzz.rb

# coding: utf-8
(1..100).each do |n|
  puts case
  when n % 15 == 0
    'FizzBuzz'
  when n % 3 == 0
    'Fizz'
  when n % 5 == 0
    'Buzz'
  else
    n
  end
end

fizzbuzz2.rb

# coding: utf-8
(1..100).each do |n|
  fb = ''
  fb << 'Fizz' if n % 3 == 0
  fb << 'Buzz' if n % 5 == 0
  puts (fb.empty? ? n : fb)
end

fizzbuzz3.rb

# coding: utf-8
class Numeric
  def divided_by?(n)
    self.modulo(n).zero?
  end
end

def fizzbuzz(n)
  fb = ''
  fb << 'Fizz' if n.divided_by?(3)
  fb << 'Buzz' if n.divided_by?(5)
  fb.empty? ? n : fb
end

(1..100).each{|n| puts fizzbuzz(n)}